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  • Articles  (3)
  • 2015-2019  (3)
  • 2005-2009
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  • 1
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    Influence of plankton community structure on the sinking velocity of marine aggregates (2016)
    Wiley
    In:  EPIC3Global Biogeochemical Cycles, Wiley, 30(8), pp. 1145-1165, ISSN: 0886-6236
    Details
    Publication Date: 2019-07-17
    Description: About 50 Gt of carbon is fixed photosynthetically by surface ocean phytoplankton communities every year. Part of this organic matter is reprocessed within the plankton community to form aggregates which eventually sink and export carbon into the deep ocean. The fraction of organic matter leaving the surface ocean is partly dependent on aggregate sinking velocity which accelerates with increasing aggregate size and density, where the latter is controlled by ballast load and aggregate porosity. In May 2011, we moored nine 25 m deep mesocosms in a Norwegian fjord to assess on a daily basis how plankton community structure affects material properties and sinking velocities of aggregates (Ø 80–400 µm) collected in the mesocosms' sediment traps. We noted that sinking velocity was not necessarily accelerated by opal ballast during diatom blooms, which could be due to relatively high porosity of these rather fresh aggregates. Furthermore, estimated aggregate porosity (Pestimated) decreased as the picoautotroph (0.2–2 µm) fraction of the phytoplankton biomass increased. Thus, picoautotroph-dominated communities may be indicative for food webs promoting a high degree of aggregate repackaging with potential for accelerated sinking. Blooms of the coccolithophore Emiliania huxleyi revealed that cell concentrations of ~1500 cells/mL accelerate sinking by about 35–40%, which we estimate (by one-dimensional modeling) to elevate organic matter transfer efficiency through the mesopelagic from 14 to 24%. Our results indicate that sinking velocities are influenced by the complex interplay between the availability of ballast minerals and aggregate packaging; both of which are controlled by plankton community structure.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 2
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    Ocean acidification does not alter grazing in the calanoid copepods Calanus finmarchicus and Calanus glacialis (2016)
    OXFORD UNIV PRESS
    In:  EPIC3ICES Journal of Marine Science, OXFORD UNIV PRESS, 73(3), pp. 927-936, ISSN: 1054-3139
    Details
    Publication Date: 2017-06-07
    Description: It is currently under debate whether organisms that regulate their acid–base status under environmental hypercapnia demand additional energy. This could impair animal fitness, but might be compensated for via increased ingestion rates when food is available. No data are yet available for dominant Calanus spp. from boreal and Arctic waters. To fill this gap, we incubated Calanus glacialis at 390, 1120, and 3000 µatm for 16 d with Thalassiosira weissflogii (diatom) as food source on-board RV Polarstern in Fram Strait in 2012. Every 4 d copepods were subsampled from all CO2 treatments and clearance and ingestion rates were determined. During the SOPRAN mesocosm experiment in Bergen, Norway, 2011, we weekly collected Calanus finmarchicus from mesocosms initially adjusted to 390 and 3000 matm CO2 and measured grazing at low and high pCO2. In addition, copepods were deep frozen for body mass analyses. Elevated pCO2 did not directly affect grazing activities and body mass, suggesting that the copepods did not have additional energy demands for coping with acidification, neither during long-term exposure nor after immediate changes in pCO2. Shifts in seawater pH thus do not seem to challenge these copepod species.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 3
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    Biological responses to ocean acidification (2018)
    Arctic Monitoring and Assessment Programme (AMAP), Tromsø, Norway
    In:  EPIC3AMAP Assessment 2018: Arctic Ocean Acidification, Arctic Monitoring and Assessment Programme (AMAP), Tromsø, Norway, pp. 15-28, ISBN: 978-82-7971-1
    Details
    Publication Date: 2018-11-09
    Repository Name: EPIC Alfred Wegener Institut
    Type: Inbook , peerRev
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